Method of making laminated structures



Juiy 13, 1948- c. N. CONE METHOD OF MAKING LAMINATED STRUCTURES Filed March 14, 1941 0155 N. come- Patented Jul 13, 1948 METHOD OF MAKING LAIMINATED STRUCTURES Charles N. Gone, Portland, reg., asslgnor to M and M Woodworking Company, Portland, Oreg.,

a corporation of Oregon Application March 14, 1941, Serial No. 388,294

3 Claims.

.1 This invention relates to construction material, and has particular reference to a method of covering the surface of wood veneers with a sheet of "fibrous, cellulosic material, felted together into a sheet of paper and bonded to the surface of the wood by a thermoplastic, water repellent material.

The products of the invention are laminated or ply structures having particular usefulness as wallboard or panels.

The panels created by this method possess a smooth, polished surface which is homogeneous and neutral in character, and which, being absorbent, furnishes, in the language of painters and decorators, a tooth for paint, kalsomlne, etc. If wall paper is to be applied, the surface of the panel is capable of absorbing moisture from the wall paper paste, causing it to set and hold the paper to the wall.

The surface of the panel is composed of two elements. The outer element consists of a sheet of fibrous, cellulosic material, felted together into a sheet of paper. The inner element of the surface coating may be asphalt. Being thermoplastic, it is capable, when made fluid or semi-fluid by an elevated temperature, of conforming to the.

irregular surface of the wood and of penetrating sufficiently into the cellular'structure of the wood comprising two plies of wood veneer and the hereinbefore mentioned surface elements.

Figure 5 is a fragmentary elevation of a panel comprising three plies of wood veneer and the hereinbefore mentioned surface elements.

Figure 6 is a generally schematic elevation of a modified form of mechanism which also may be employed in the practice of the invention.

Plywood is made of three or more plies of wood veneer with the grain of each ply of veneer running at right angles to the grain of each adjacent ply of veneer, the plies being bonded together to form a panel having great strength, rigidity and flatness. These are important properties in wallboard, but equally important i the character of the surface of the panel. An ideal surface is one which is homogeneous and neutral in character; that is, one capable of receiving the largest possible variety of different finishes or decorative effects, as, for example, paint, enamel, kalsomine, wallpaper, etc.

In the presently disclosed method of treating wood veneer panels, the faces of the panels are neutralized and rendered most favorable for the application thereto of paint, kalsomine or wall-. paper. Each panel is made of a core member consisting of rotary cut wood veneers, and a laminated surface composed of two elementsadhesively united to the core member interfacially. The outer surface element consists of a sheet of fibrous cellulosic material, felted together into a are completely hidden by a neutral and acceptable surface for painting, kalsomining, or papering.

It is an object of the invention to provide a neutral surface for wood veneer panels to which paint or enamel can be applied in the ordinary manner, and which will not reveal the pattern of the grain of the wood.

It is a further object of the invention to provide a method for covering panels of rotary cut wood veneers to provide a homogeneous neutral surface therefor.

Additional objects and advantages of the invention will become apparent from a perusal of the following description of the novel steps of manufacture and of the unique combination of elements constituting the improved panels herein described. The method is illustrated by a drawing in which:

Figure l is a generally schematic elevation of a device intended for use in the practice of the invention.

Figure 2 is a fragmentary elevation of the platens between which the panel is conveyed at the time of fabrication, the figure illustrating the pitch of the working surfaces of the platens.

Figure 3 is a fragmentary elevation of a panel comprising one ply of wood veneer and the above mentioned surface elements.

Figure 4 is a fragmentary elevation of a panel the time of contact permits it to conform to the irregular surface of the wood and to fill and seal existing openings in the wood. such as splits,

checks or knotholes. A sumcient amount of asphalt is applied to compensate for irregularities in the surface of the wood and so permit the sheet of paper to lie perfectly fiat. This flat surface,

once produced, is notdisturbed by movement of panel in a continuous web. Although it is cellulosic in nature and subject to shrinking and swelling due to change in moisture content, it is held rigidly in place by the film of asphalt towhich it is bonded and which in turn is bonded to the rigid wood veneer. It is desirable that the paper advantageous recovery of useful veneers.

have a smooth, hard, scuff resistant surface, and

that fibers-which tend to protrude above the surface be laidfiat. Otherwise they are likely to appear when the panelis painted. However, if such fibers do appear, a very satisfactory finish can be obtained by lightly sanding the surface after the application of an undercoat and before application of the enamel. Besides presenting a homogeneous neutral surface suitable for receiving various types of wall finishing, the layer of paper contributes consideran endless length or assembly across the direction of the grain can be obtained by laying together miscellaneous widths of veneers so that the joint in one ply never coincides with the joint in the opposite ply.

Figure 4 of the drawings illustrates a panel having a two ply veneer core, the loose surfaces of the plies being bonded together with their grains parallel. In this construction the wood veneers l-l may be cut to only on half the thickness of the veneer used in a panel using a single ply wooden core. The thinner veneers are cut on the lathe with less shattering of the veneer, and a material saving is accomplished in the drying time. The completed panel comprises a core member made of the veneers 4-4, layers of asphalt 55, and surface layers of paper 6-6.

, When a force is applied tending to bend this astageously utilized and hence adds considerably to the resistance of the panel to deflection.

Because of the high tensile strength of paper. it is admirably adapted for use as an important structural element in a new type of laminated structural material. This consists of a single central ply of wood veneer covered on each side with a layer of asphalt upon which is superimposed a layer of paper. trated in Figure 3, and consistsof surface plies of paper I and asphalt 2. and a core of wood The structure is i1lus-- veneer 3. The layers of asphalt and paper are relatively thin, the bulk of the thickness of the structure being the wooden core. The wood supplies ample strength in the direction of its grain, but is comparatively weakacross the grain. A

high degree of strength across the grain of the wood is supplied to the panel by the outer layers of paper, due to its relatively high tensile strength. A laminated structure such as illustrated in Figure 3 may be used wherever its strength across the grain is sufllcient to withstand the stresses imposed thereon. As illustrative of such uses, a panel having a core member consisting of a single ply veneer supplies sufficient rigidity for packaging material, drawer bottoms, mirror backs, etc. The greater degree of tensile strength in a piece of rotary cut veneer resides in the very outer surface of the tight side of the veneer. A sheet of wood veneer wil1 bend much more easily toward the tight side of the veneer than toward the loose side, for the reason that the loose side is shattered and full of checks produced when the veneer was peeled from the log and therefore, offers little resistance to tension.

In practice it is found necessary in rotary cut veneer to clip the veneers to miscellaneous lengths to eliminate defects and obtain the most It is found that if two pieces of veneer are simply abutted in edge to edge relation to form the central ply for the panel, the joint will show through the paper facing. Only by edge gluing these joints can this be prevented. A slightly different type of assembly has proved a means of eliminating this defect and at thesame time produces a panel which has two tight sides. This is accomplished by making the core of two plies of rotary cut veneer glued together with their grain parallel and with the two.loose sides bonded together so that both sides of the core present a tight, and mechanically strong surface. Also this assembly permits overlapping or staggering of joints; and

sembly in a direction across the grain of the veneers, this force is resisted by the tensile strength of the paper on the one side of the assembly and by th resistance to compression of the outer surface of the veneer member on the other side of the assembly. If the veneer is sanded, this outermost tight layer of the wood is removed and the sanded surface of the veneer has less resistance to compression than the unsanded surface. Therefore, the panel built with unsanded veneers has more resistance to bending and lies flatter than will a comparable panel made with sanded veneers.

The structure illustrated in Figure 5 comprises a panel having a plywood core I made of three plies of wood veneer with the grain of each ply of veneer running at right angles to the grain of each adjacent ply of veneer, the plies being bonded together to form a panel having great strength, rigidity and flatness. Ordinarily the first step in finishing a plywood panel is to give it a smooth surface, usually by sanding. In the present construction a smooth polished surface is obtained without sanding the wooden core. This is of considerable advantage in retaining the full structural strength of the wood veneer elements of the assembly. While this advantage is more pronounced wherethe core of the panel consists of twoplies of rotary cut veneer glued together with their grains parallel, as illustrated in Figure 4, nevertheless the elimination of the step of sanding the panels avoids considerable expense. Moreover, the surface produced by the sanding operation, which may appear to be smooth and level, actually shows in relief the pattern of the grain. This is due to the fact that the hard summer wood resists the cutting action of the sand paper and is forced below the surface by compression of the layer of softer spring wood which underlies it. Even though the surface may be perfectly flat when the panelcomes from the sander, the compressed wood cells will in time reheld rigidly apart the exact distance which is required to produce the desired thickness of the panel. As the leading edge of the core member enters between these surfaces the ends of sheets of paper are also led between the surfaces, one sheet of paper overlying each face of the core member passes between the opposed surfaces, sufiicient pressure is exerted by'the assembly against the surfaces to make a bonding contact between the asphalt andthe surface of the wood, and to bond the paper thereto in a smooth plane surmounting the film of asphalt. The plasticity of the film of asphalt at the time of contact insures, first, the conformation of the asphalt to the irregular surface of the wood, and, second, the perfect leveling of the sheet of paper surmount ing the film of asphalt. This plasticity of the asr phalt is due to its elevated temperature. When it cools it becomes comparativelyrigid. Contact with the cold plywood cools the thin film of asphalt so rapidly that it is non-fluid when the assembled panel is discharged from between the opposed surfaces, and it binds the paper to the core member, holding the paper in a level position superimposed over the irregular surface of the wood.

Referring to Figure l of the drawings, feed rolls 8--8 are shown as feeding a plywood core g member 9 between an upper platen l 0 and a lower platen II. The platens Ill and H are heated, particularly adjacent the edge thereof which initially engages the core member. Heating elements I2-l2 are shown as being mounted in the ends of the platens, although in actual practice an addednumber of heating elements may be mounted in each platen. The platens are of a width equal to the width of the completed panel and, as has been stated, their opposed surfaces l3--|3 are smooth and highly polished. It may.

be desired to pitchthe surfaces of the platens toward each other, with the narrowest point of the-opening therebetween occurring at the rear or discharge edge of the opening. The distance between the platens at this narrowest point determines the thickness of the panel, the tendency being to progressively flatten the panel by means of the pressure exerted thereupon by the converging surfaces of the platens. The action of the platens is to iron the panel, the asphalt remaining sufficiently plastic, by reason of the heated platens, to compensate for irregularities in the surface of the core member and form a level base for the paper.

Mounted above the platen. I0 is a roll of paper l4 from which the paper is unrolled in a continuous sheet and fed between the platen Ill and the upper face of the core member 9. The sheet of paper l4 passes over the end of the platen H) in such a manner as to form one side of a trough l5 adapted tobe filled with asphalt in a fluid condition. A heatingelement I6 is mounted in one wall of the trough I5 and extends lengthwise 0f the trough to maintain the fluidity of the asphalt. The trough I5 is provided with ends and a side wall, but the bottom thereof is formed by the advancing core member 9. Asphalt is not supplied to the trough until after the end of the core member 9 has comeinto registry therewith. The side wall I! of the trough is made to slope toward the point where the sheet of paper i4 is brought into overlying relation with the core member 9, at which point the fluid asphalt is 6 1 permitted to flow onto the core member and into the space between it and the paper la. The travel of the paper forming one wall of the trough and the forward movement of the core,

l8 from which the paper is unrolled in a continuous sheet and fed between the platen H and the underside of the core member 9. The sheet of paper passes upwardly over the end of the platen I I in such manner as to form one side wall of a trough 2c adapted to be filled with asphalt in a fluid condition. A heating element 2| is mounted in the trough :and extends lengthwise thereof to maintain the asphalt at the desired temperature. The upward movement of the paper forming one wall of the trough serves to coat the upper surface of the paper and to pull the fluid asphalt into the space between the paper and the core member in sufllcient quantity to fill existing openings in the lower surface of the core and to press the paper against the surface of the platen H. An applicator roller 22 may be mounted for rotation within the trough for applying the asphalt to the underside of the core member.

Experience teaches that'the use of the device just described tends to produce panels having a heavier film of asphalt on the upper side of the core member than on the lower side, for the obvious reason that greater quantitie'sof the melted asphalt will flow from the trough i5 onto the upper side of the core member than can be applied to the under side of the core member from the trough 20. It may be preferable, therefore, to apply the laminated surface structure to one side of the core member at a time, and so insure that the two applied surfaces will be of equal thickness. This may be accomplished by feeding the core member between two plane surfaces held rigidly apart a distance less than the desired thickness of the panel but greater than the thickness of the core member. The under side of the core member is then caused to rest upon the lower platen, the distance between the upper surface of the core member and the upper platen being equal to the desired thickness of the surface to be applied. The leading edge of the corememher and the end of a continuous web of paper is then fed between said platens simultaneously, the paper overlying the core member. Thereupon asphalt, in a fluid condition, is caused to flow into the space between the sheet of paper and the core member in sufficient quantity to press said sheet of paper tightly against the platen and so produce a level surface surmounting the film of asphalt. By then inverting the panel and running it through the device again, a laminated surface structure may be applied to the opposite side of the core member in a. similar manner, it being understood that the spacing between the two platens should be correspondingly widened.

The foregoing method of application of the surface elements to the faces of the core member is particularly effective where the core member is made up of rough, unsanded veneers, or veneers containing splits, checks and knotholes; it being appreciated, of course, that veneers showing these defects have not heretofore been used as face piles on plywood panels. Where, however, the surface elements are to be applied to sound panels the asphalt may be applied in a uniform layer to one side of the sheet of pap This can be done by the use of feed rolls and scrapers in a well known manner. The web of paper, coated on one side with melted asphalt, is rolled onto the surface ofthe wood panel, the asphalt coming in contact with the wood while it is still hot and fluid enough to make a binding contact with the wood. The assembly of paper, asphalt and plywood may then be passed between a pair of rollers which apply suillcient pressure to make a bonding contact between the asphalt and the surface of the wood and lay the paper down in a smooth plane surmounting the plastic 111m of asphalt.

Figure '6 shows a schematic elevation of a mechanism by means of which this operation can be carried out. The drawing illustrates continuous webs ofpaper 23 as passing over' applicator rolls 24 which revolve in troughs 25 filled with asphalt 26 in a fluid state. Asphalt is applied to one side, of each sheet of paper by the applicator rolls, and the assembly of paper 23, asphalt 26, and core member 21 passes between a pair of rolls 23 which apply sufficient pressure to create a bond between the asphalt and the surface of the wood and lay the paper down in a smooth plane surmounting the film of asphalt. The pressure rolls 28-hold the assembly fiat inthe direction of the length of the rolls, but not in the direction perpendicular to the rolls. Some means for flattening out the assembly in the direction in which it is moving may be required, and for this purpose platens 29 are provided, these being held rigidly apart the exact distance which is required for the thickness of the panel. It is preferable that the platens be pitched toward each other, and that the be heated, to cause the asphalt to conform to irregularities in the surface of the wood and to produce a perfect leveling of the paper which is bonded thereto.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. The method of treating the surface of wood veneers to provide a homogeneous and neutral surface therefor, comprising heating an anhydrous thermoplastic adhesive material to a degree to render said material sufficiently plastic to create a satisfactory bond with the wood, applying said material while in said heated condition to the surface of the wood in sufficient quantity to fill and seal existing openings in the wood and to provide a flat level surface over irregularities existing in the surface of the wood, simultaneously applying a sheet of paper over said material, and smoothing said paper while said material is in a plastic state to create a flat level surface for the structure.

2. The method of treating the surface of wood veneersto provide a homogeneous and neutral surface therefor, comprising heating. an anhydrous thermoplastic adhesive material to a degree to render said material sufficiently plastic to create a satisfactory bond with the wood, applying said material while in said heated condition to the surface of the wood in sumcient quantity to provide a flat level surface overlying irregularities in the surface of the wood, applying a sheet of paper over said material while said material is plastic, and smoothing said paper while said material is in a plastic state to create a flat level surface-for the structure.

3. The method of treating the surface of wood veneers to provide a homogeneous and neutral surface therefor, comprising heating asphalt to a degree to render said asphalt sufliciently plastic to create a satisfactory bond with" the wood, applying said asphalt while in said'heated condition to the surface of the wood in suiiicient quantity to compensate for irregularities in the surface of the wood and to provide a flat level surface thereover, applying a sheet bf' paper over said asphalt while said asphalt is plastic, 4 d smoothing said paper while said asphalt s a plastic state to create a flat level surface or the structure.

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REFERENCES CITED The following references are of record in the file of this patent: 

